Thanks. This is a nice thread with some great information and discussion.
Originally Posted by Shorty Cox
...the one 15,000 BTU unit didnít quite do an adequate job. As Kitty stated, the unit we had did not have enough BTUís to cool a BUT the size of a TUB!!!
.... I then ordered a 13,500 Coleman AC unit. (No heat) I received the AC unit last Monday, April 29th.
I would like to point out that the HVAC designers felt that a 15,000 BTU unit was adequate for the size and design of the trailer. Adding a 13,500 BTU unit to the existing 15,000 BTU unit is close to doubling the capacity. That is likely overkill for any ambient temperature and humidity anyone is going to encounter in North America.
Comfort air conditioning is rarely sized for the absolute highest ambient temperature and humidity which is expected. To design for worst case conditions is neither economical or good for the environment. One of the important things that happens for comfort air conditioning is that the humidity gets removed as the air conditioning unit cools the temperature. If the temperature is reduced too quickly the humidity is not reduced and you get a clammy uncomfortable environment.
For many people it may only be necessary to add some fans to move the air around in the trailer to reduce hot spots. Fans are much cheaper to purchase and operate.
I don't know what the available standard size units are for trailer rooftops. I suggest that anyone who is considering an additional A/C unit for their trailer should consult someone familiar with sizing air condtioners before going out and buying a unit to install. In my opinion a smaller sized unit will do the job at less cost.